The common denominator of trading caravans
and migratory birds is that both use deserts only
as corridors linking non-desert starting points with
non-desert destinations. however, while using the
desert corridor, both often interact with the desert
environment, its biota and its human population.
And, just as desert corridors have been used by
armies to reach their non-desert destinations for
assault, so it is often the case with locusts that use
deserts as a corridor for invading non-desert areas.